See an interesting chart,
almost contemporary (1923), showing a proposed
relationship between dress length, etc., and
painful menstruation, in Woman's
Physical Freedom, a book by Clelia Duel
Mosher, M.D., and read a discussion
of dress length and bodily functions, on
this site.

Open-seat underpants (see drawings
of an older pair showing how they
"worked") enabled women to easily
urinate and defecate without having to
reach under their dresses to pull down
or remove anything. It also allowed
them to wear a menstrual belt and pad
over their underpants, since the pad
could pass through the opening (see a
German drawing
from 1888). That's my theory, anyhow.

Open seats had at least two
disadvantages. They didn't

2. conceal
the genitals if the
clothing rose high enough, or if the
observer was low enough, or both;
concealment seems to have been the
main reason underpants came into
being.

But after World War I dresses became
shorter and less bulky, making
closed-crotch underpants - still long;
they seem not to have become short and
tight until the mid 1930s -
unnecessary, so the crotches closed.

This 1922 catalog, in a transitional
period, might be one of the last one
to sell open-seat underpants. Some
one-piece underwear covering most of
the body has retained a helpful
drop-seat feature.

See an interesting chart,
almost contemporary (1923), showing a
proposed relationship between dress
length, etc., and painful
menstruation, in Woman's Physical
Freedom, a book by Clelia
Duel Mosher, M.D., and read a discussion
of
dress length and bodily functions,
on this site.

Below:
Open-seat (crotchless) drawers from
probably right before 1900. See more details.

Dress from the catalog.

"A particularly smart
frock which reflects in every line the
latest New York style," reads the ad
copy for the first dress (and in
color) in this 1922 catalog. On the
same page we read, "Our own fashion
experts, living in New York all the
year round, and studying the styles,
have selected for you the best of
everything new this season. If you
select a dress from these pages you
know positively in advance that you
are to have the pleasure of wearing an
authoritative new style."

Women could maneuver
better in the dresses of 1922 and
decreasingly needed the convenience
and disadvantages of an open seat.

Right:
Enlargement from the dress ad. This is
typical of the dreamy, seductive
drawings of houses of the time in
America.